/**
 * 给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。
 * 岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。
 * 此外，你可以假设该网格的四条边均被水包围。
 * 
 * 输入：
 * 输入：grid = [
    ["1","1","1","1","0"],
    ["1","1","0","1","0"],
    ["1","1","0","0","0"],
    ["0","0","0","0","0"]
 * ]
 * 输出：1
 */

/**
 * @param {character[][]} grid
 * @return {number}
 */
var numIslands = function (grid) {
    const m = grid.length;
    const n = grid[0].length;

    let visited = new Array(m).fill(false).map(() => new Array(n).fill(false));
    let res = 0;

    const dirs = [[1, 0], [0, 1], [-1, 0], [0, -1]];
    let dfs = (grid, visited, x, y) => {
        for (let i = 0; i < 4; i++) {
            let nextx = x + dirs[i][0];
            let nexty = y + dirs[i][1];

            if (nextx >= 0 && nextx < m && nexty >= 0 && nexty < n) {
                if (!visited[nextx][nexty] && grid[nextx][nexty] === "1") {
                    visited[nextx][nexty] = true;
                    dfs(grid, visited, nextx, nexty);
                }
            } else {
                continue;
            }

        }
    }

    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            if (!visited[i][j] && grid[i][j] === "1")  {
                visited[i][j] = true;
                res++;
                dfs(grid, visited, i, j);
            }
        }
    }
    return res;

};